Non-destructive (NDE) imaging structural evaluation tools are able to detect linear features and other stress related deformities in structures, such as aircraft, in their early propagation stages before they reach critical size. Many of these small, often undetectable linear features produce a very low pixel signal strength difference over a couple of pixels relative to the surrounding structural material, thus necessitating a need to enhance their detectability and improve their inspection. X-ray backscatter imaging technology is one non-destructive structure evaluation tool that may image and detect quantifiable linear features, while other non-destructive structural analysis tools may be used, such as borescopic imaging of surface linear features during limited access inspections and photographic optical imaging of surface linear features on structures.
One way to improve signal-to-noise ratios for small flaw detection for x-ray backscatter methods is to improve the photon count statistics at the detectors by allowing more time to collect the signal. This is done by slowing down the system scanning speed which can significantly increase the inspection times making this approach impractical. It may also not improve linear crack detection since increasing the photon count alone (by slowing down a scan) improves the signal-to-noise only in the linear range of a detector, beyond which saturation occurs and crack detectability cannot be improved. There are various image enhancement methods that smooth or connect features, or enlarge them in the image plane, that increase the noise at the same time they increase the signal, thereby preventing any enhancement of linear feature detectability.
There is a need for increasing the pixel signal strength produced by linear cracks, while at the same time, smoothing or reducing the noise of the pixel signal intensity of the surrounding structural image pixels. It is with respect to these and other considerations that the disclosure herein is presented.